Integumentary System (Chapter 5) Lecture Materials for Amy Warenda Czura, Ph.D. Suffolk County Community College Eastern Campus

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1 Integumentary System (Chapter 5) Lecture Materials for Amy Warenda Czura, Ph.D. Suffolk County Community College Eastern Campus Integument = covering ~16% of body mass: ~2 meter 2 Primary Sources for figures and content: Marieb, E. N. Human Anatomy & Physiology 6th ed. San Francisco: Pearson Benjamin Cummings, Martini, F. H. Fundamentals of Anatomy & Physiology 6th ed. San Francisco: Pearson Benjamin Cummings, Composed of: 1. Cutaneous membrane A. Epidermis - superficial epithelium B. Dermis - underlying CT w/ blood supply 2. Accessory structures A. Hair B. Nails C. Exocrine glands Functions: 1. Protect underlying tissues from infection, exposure and dehydration 2. Excrete salts, water, and organic waste 3. Maintain normal body temp (conserve and radiate heat) 4. Synthesize Vitamin D3 for calcium metabolism 5. Store nutrients (fat) 6. Sensory detection: touch, pressure, pain, and temp Epidermis (on handout) Amy Warenda Czura, Ph.D. 1 SCCC BIO130 Chapter 5 Lecture Notes

2 The corrugated border between dermis and epidermis helps bond epidermis to dermis (increased surface area for attachment) In thick skin epidermal ridges show on the surface as fingerprints: function to enhance gripping Epidermis water resistant but not water proof: Insensible perspiration = water loss through epidermis: ~500ml (1 pint) / day (more if damaged, e.g. burn) Callus = thickening of epidermis, due to repeat friction Blister = separation of epidermal layers or epidermis from dermis, space fills with interstitial fluid Skin Color Pigment based: epidermal pigments and blood pigments contribute to the color 1. Epidermal Pigmentation A. Carotene: yellow-orange, from diet -converted into Vitamin A -localized to epithelium -functions in normal maintenance of epithelia and photoreceptors -excess accumulates in stratum corneum B. Melanin: brown, from melanocytes -for UV protection Melanocytes: in stratum basale -synthesize melanin from tyrosine (amino acid) -packaged in melanosomes -transferred to cytoplasm of keratinocytes -cluster around top side of nucleus -eventually digested by lysosomes Everyone has ~1000 melanocytes /mm 2 : -pale people: small melanosomes, present only in stratum basale and spinosum -dark people: larger, greater number of melanosomes, retained up through stratum granulosum Freckle = overproduction of melanin from single melanocyte UV exposure: -some needed for Vitamin D3 production -excess = damage (DNA mutation) -fibroblasts! altered CT structure, wrinkles -epidermal cells, melanocytes! cancers: squamous cell carcinoma melanoma Amy Warenda Czura, Ph.D. 2 SCCC BIO130 Chapter 5 Lecture Notes

3 2. Dermal Circulation: hemoglobin pigment -oxygenated blood = red color, hemoglobin in RBCs, through skin looks pink *vasodilation! skin looks more red *vasoconstriction! skin looks more pale -Cyanosis = low oxygen, blood deep purple, skin appears blue/purple results from low temp, heart failure, asthma Abnormal skin color: -Jaundice: liver fails to excrete bile, accumulates in skin, yellow -Addison s Disease: pituitary secretes excess adrenocorticotropic hormone, stimulates melanocytes, excess melanin, bronzing -Albinism: genetic mutation in melanin biosynthesis pathway, lack pigmentation in skin, hair and eyes -Vitiligo: autoimmune disease! destruction of melanocytes Vitamin D3 Production: Cells of stratum spinosum and basale UV energy + cholesterol = Vitamin D3 Vitamin D3 used by kidney to synthesize the hormone calcitriol Calcitriol necessary to signal small intestine to absorb calcium No VitD! no calcitriol! no calcium absorption! weak bones Dermis (on handout) Collagen fibers from reticular layer blend into papillary and subcutaneous layers to attach integument to body -wrinkles = dermis stretched beyond its elastic capacity, collagen fibers damaged -stretch marks = collagen & elastic fibers torn -collagen & elastin fibers arranged in parallel bundles aligned to resist the expected direction of force = lines of cleavage -cuts parallel to lines of cleavage will heal faster and with less scar than those perpendicular Dermis highly vascularized: must feed itself and epidermis above Contusion = bruise, trauma that ruptures blood vessels but does not break skin, blood pools in dermis and must be removed by phagocytes (slow process) Amy Warenda Czura, Ph.D. 3 SCCC BIO130 Chapter 5 Lecture Notes

4 Sensory perception in integument Skin highly innervated for sensory perception, mostly in dermis: 1. Tactile discs/merkel cellsdeep layers of epidermis, superficial touch 2. Free nerve endings - superficial dermis, pain and temperature 3. Tactile/Meissner s corpuscles - superficial dermis, light touch 4. Lamellated/Pacinian corpuscles - deep dermis, pressure and vibration Subcutaneous Layer a.k.a. Hypodermis -areolar and adipose CT -tightly interwoven with reticular layer of dermis -not part of cutaneous membrane -stabilizes position of skin while permitting independent movement of skin and muscles -children: even layer of adipose -puberty: adipose shifts male: neck, arms, abdomen, lower back female: breast, buttocks, hips, thighs -no vital organs: safe for SubQ injection, vascular for quick absorption Accessory Structures of the Integument: 1. Hair follicles and hair 2. Sebaceous glands 3. Sweat glands 4. Nails All of these structures are anchored in the dermis but are derived from epidermal tissue Hair Human body: ~2.5million hairs, 75% on body Everywhere except: palms, soles, lips, and certain genitalia Hair itself is dead, but is derived from live epidermal tissue Hair and Hair Follicle Structure (on handout) Hair follicle Glassy Membrane Hair Matrix Amy Warenda Czura, Ph.D. 4 SCCC BIO130 Chapter 5 Lecture Notes

5 Shape of the shaft determines feel: -flattened shaft = kinky hair -oval shaft = silky and wavy hair -round shaft = straight and often stiff hair Two types of hair produced: 1. Vellus hairs = peach fuzz, -lacks medulla -covers body, at puberty hormones can trigger switch to terminal hairs 2. Terminal hairs -thick, coarse, pigmented -all three layers Hair Color -range yellow to black due to melanin from melanocytes in hair matrix -red: iron added -melanin stored in cortex and medulla With age, melanin declines, air pockets in medulla increase = gray or white hair Hair Growth ~0.33mm/day, not continuous: cycle of growth and rest 1. Active phase: new hair added to hair root by dividing cells of hair matrix (weeks-years) 2. Regressive phase: cells of hair matrix stop dividing, hair root and hair papilla separate loose hair = club hair 3. Resting phase: cells of hair matrix and hair follicle remain inactive (1-3 months) New active phase begins Hair length differences = difference in time spent in active phase: eyebrows = few months head = many years During hair growth nutrients and toxins are incorporated into hair: history of exposure Alopecia = shift from terminal hair to vellus hair, thinning/balding, some degree expected with age Male pattern baldness = genetic alopecia, early age onset Treatments: aimed at converting vellus hairs to terminal hairs Hair removal: -difficult to achieve permanent result -any remaining matrix cells can regenerate all hair follicle structures Hair Functions: Head: -UV protection -cushion from trauma -insulation Nostrils, Ears canals, Eyelashes: -prevent entry of foreign material Amy Warenda Czura, Ph.D. 5 SCCC BIO130 Chapter 5 Lecture Notes

6 Body hair: sensory detection Root hair plexus: sensory nerves at base of hair follicle that detect slight movement of hair Arrector pili muscle: -attached to every hair follicle -contract to stand hair perpendicular to skin surface (goose bumps) -smooth muscle: involuntary Integumentary Glands -All are exocrine glands (secrete product onto skin surface via a duct) 1. Sebaceous glands -holocrine secretion -secrete sebum into hair follicle sebum=lipids+cholesterol+ proteins+electrolytes function: -lubricate and protect keratin -prevent evaporation -inhibit bacterial growth Sebaceous glands active in fetus, then off until puberty, on whole adult life Acne = inflammation of a sebaceous gland, usually due to bacterial infection 2. Sudoriferous glands / Sweat glands A. Merocrine/Eccrine sudoriferous glands - 2 to 5 million all over body - produce sensible perspiration: 99% water + electrolytes + organic nutrients + antibodies + antimicrobial agents + organic wastes - merocrine secretion - small coiled tubular glands - located in superficial dermis - open directly on surface of skin -secrete in response to high temp or stress Functions of sensible perspiration: 1. Evaporative cooling of surface of skin to reduce body temp 2. Excrete waste electrolytes and drugs 3. Protection A. Prevent adherence of microbes (antibodies) B. Physically wash off microbes C. Antimicrobial agents to kill microbes dermicidin (antibiotic) Amy Warenda Czura, Ph.D. 6 SCCC BIO130 Chapter 5 Lecture Notes

7 B. Apocrine sudoriferous/sweat glands -merocrine secretion -armpits, nipples, groin -secrete into hair follicle -secretion is sticky and cloudy: sensible perspiration + proteins + lipids -microbes eat it! wastes = body odor -glands deep in dermis -surrounded by myoepithelial cells: contract in response to sympathetic nervous system stimulation -active only after puberty Special apocrine sweat glands: 1. Mammary glands -located in female breast -secrete milk during lactation 2. Ceruminous glands -located in external ear canal -secrete cerumen Integumentary gland control: -merocrine sudoriferous glands can be turned on and off in localized regions in response to temperature or emotions -sebaceous and apocrine sudoriferous glands are either all on (body wide) or all off, no local control Nails -scale like projections on dorsal surface of distal digits -functions: protect tips from mechanical stress, assist gripping -consists of dead cells containing hard keratin -new nail formed at nail root -nail growth is continuous Injury and Repair -integument can function independent of nervous and endocrine systems to maintain own homeostasis -mesenchymal cells of dermis can regenerate connective tissue -germinative cells (basal cells) of epidermis can regenerate epithelial tissue Amy Warenda Czura, Ph.D. 7 SCCC BIO130 Chapter 5 Lecture Notes

8 Integumentary Injury Repair (on handout) -repair may end up like original tissue or -keloid = thick area of scar tissue covered by smooth epidermis Burns: -First Degree Burn: damage to surface of epidermis, heals on own -Second Degree Burn: damage to epidermis and superficial dermis, heals on own -Third Degree Burn: damage to whole cutaneous layer (epidermis, dermis, accessory structures), granulation tissue cannot form thus no healing Requires skin grafts or living bandages Burn >20% of body can kill It affects: 1. Fluid and electrolyte balance 2. Thermoregulation 3. Protection from pathogens Age Related Changes: 1. Stem cell activity declines: skin thin, repair difficult 2. Epidermal dendritic cells decrease: reduced immune response 3. Vitamin D3 production declines: calcium absorption declines! brittle bones 4. Glandular activity declines: skin dry, body can overheat 5. Blood supply to dermis declines: tend to feel cold 6. Hair follicles die or produce thinner hair (terminal! vellus) 7. Dermis thins and becomes less elastic! wrinkles 8. Sex characteristics fade: fat deposits spread out, hair patterns change Amy Warenda Czura, Ph.D. 8 SCCC BIO130 Chapter 5 Lecture Notes